In networking systems, routers and/or switches typically move packets of information from one of a number of input ports to one or more output ports. In many applications, such as multicasting, a packet may need to be duplicated on multiple output ports. Further, for support of Virtual Local Area Network (VLAN or “Vlan”) systems, a packet may need to be duplicated according to a wide variety of possibilities. In a typical Vlan system, 12-bits may be used to indicate a particular Vlan, so the number of possible distinct Vlans that need to be supported in the system can be as high as 4096. These requirements pose a challenge to architect the multicast packet duplication logic for Vlan systems where up to about 4K distinct Vlans can be supported per port while also maintaining the minimum duplication requirements.
A block diagram of a conventional router/switch port arrangement used for packet duplication for Vlan systems is shown in FIG. 1 and indicated by the general reference character 100. In FIG. 1, an Internet Protocol MultCast (IPMC) type packet is received by Router/Switch 102 at input port or interface X. The output ports or interfaces include port 0 requiring 3 duplicates of the packet, which are designated for Vlan2, Vlan8, and Vlan9. Output port 1 in this example only requires one duplicate for Vlan5. Output port N requires 2 duplicates: one for Vlan4 and one for Vlan7. The duplication possibilities could range from 2K times on one interface, 3K on another, 3K on another, or just one on each, for example. Further, each copy of the multicast packet can be sent to a different Vlan on a different port or multiple copies might need to be sent on each port. Accordingly, a hardware solution must be flexible enough to accommodate IPMC or other similar type packets requiring duplication on a variety of designated member ports.
Such a wide disparity of options is typically implemented in conventional approaches by simply expanding the memory used to cover all the possible cases, with little flexibility. However, such an inefficient use of memory is not desirable due to cost factors.
Consequently, what is needed is a solution that can control packet duplication in a flexible and memory efficient manner.